city, plains clothed law enforcement officers mingling in the crowds, bomb-sniffing dogs, even teams trained on weapons of mass destruction. and -- >> our dive team, our intelligence analysts will be working around the clock, our hostage negotiators. >> reporter: that fbi official spoke to us inside the multi-agency communications center, where security teams will do realtime monitoring of surveillance cameras, posted on buildings and roads. they'll also share tips and incident reports. >> reporter: with all the checkpoints, monitoring stations and other precautions, it's this stage, the parade route here along pennsylvania avenue, where the real unknown comes in. it's often along here where the president gets out of his car. >> reporter: that's when the president is most exposed and the crowds are massive. if he's right in this area and gets out of his car and walks, what's going through your mind at that moment? >> well, what's going through my mind is, you know, having faith in the plan and, you know, assuming that the agents are, you know, doing their job.